Immunohistochemical finding of α-1-antichymotrypsin in tissues of benign prostatic hyperplasia and prostate cancer

BACKGROUND: Ratio of free to total (F/T) prostate-specific antigen (PSA) is higher in the blood of patients with benign prostatic hyperplasia than those with prostate cancer. To clarify the difference between ratios in these two, alpha-1-antichymotrypsin, the major component of the bound PSA in the blood, was immunohistochemically examined. METHODS: Tissues were obtained surgically via a retropubic approach from patients with benign prostatic hyperplasia (nine cases) and prostate cancer (27 cases). These samples were processed in paraffin blocks, cut into 5 mm sections and stained with antibodies against alpha-1-antichymotrypsin and PSA. RESULTS: The percentage of alpha-1-antichymotrypsin-stained cells in prostate cancer was higher than that in benign prostatic hyperplasia (P<0.05). Almost all of glandular and cancer cells were stained with PSA antibody. The percentage of alpha-1-antichymotrypsin-stained cells in prostate cancer did not correlate to histologic grade, although alpha-1-antichymotrypsin-stained cells were more widely scattered in high grade tissues. No correlation was found between alpha-1-antichymotrypsin-stained cells and ratio of F/T in the blood of cancer patients. In about 20% of cancer tissues, histiocytes with positive alpha-1-antichymotrypsin staining were found in stroma but not in that of benign prostatic hyperplasia. CONCLUSIONS: Prostate cancer tissues are shown to have a richer environment of alpha-1-antichymotrypsin than those of benign prostatic hyperplasia. Some cancer tissues contained alpha-1-antichymotrypsin-stained histiocytes. These local events may correlate to a high amount of the bound form among total PSA in the blood of prostate cancer patients.